Method for operating a robot and robotic arm

ABSTRACT

The disclosure relates to a method for operating a robot as well as to a correspondingly operated robotic system. As part of the method, it is determined, if a difference between a current position of the robot and a target position of the robot exceeds a predetermined threshold value while the robot is in a torque-regulated operating mode. If the difference exceeds the threshold value, a predicted model-based intermediate state that the robot reaches before the target position according to the model is determined, wherein a speed of the robot in the intermediate state is lower than a predetermined speed threshold. When the robot reaches the intermediate state, the robot is automatically switched from the torque-regulated operating mode to a position-regulated operating mode. The robot then moves into the target position in the position-regulated operating mode.

The application claims the benefit of European Patent Application No. EP17185338.5, filed Aug. 8, 2017, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The disclosure relates to a method for operating a robot and to arobotic system, which may be operated accordingly.

BACKGROUND

In the field of robotics, a robot may be operated in different operatingmodes, such as a position-regulated operating mode and atorque-regulated operating mode. Each of these different modes ormethods has specific advantages and applications. A position-regulationor a position-regulated robot may offer a higher positional accuracy andmay be robust against disturbances. The position-regulated robot,however, is not suited for gripping or joining component parts or for aforce-regulated following of a predetermined path. While atorque-regulation or a torque-regulated robot solves these issues byregulating or controlling a torque or moment of force, thetorque-regulated robot in turn offers a lower positional accuracy.Torque-regulated robots are disadvantageously also prone to positionaldrifting, in particular in low stiffness settings. Additionally, withregard to disturbances, the torque-regulated robot may be especiallysusceptible to positional errors. A purely torque-regulated robot maynot be precisely and reliably positioned for gripping an object, such asa component part. A purely position-regulated robot on the other handmay not reliably non-destructively grip an object or component partwithout unrealistically precise knowledge of their exact shape andorientation. Therefore, a hybrid solution is needed.

In a conventional approach, the robot is moved into a position above thecomponent part in a position-regulated operating mode. For actuallygripping the component part, the robot is then switched to atorque-regulated operating mode only after the robot has come to acomplete rest or standstill. Therefore, the conventional approach may becostly in terms of clock cycles or a cycle time needed for complex tasksor may prohibit using or switching to a respective optimal operatingmode during tasks where the robot does not or may not come to a completestandstill.

SUMMARY AND DESCRIPTION

It is an objective of the present disclosure to enable a more flexibleswitching between different operating modes of a robot.

The scope of the present disclosure is defined solely by the appendedclaims and is not affected to any degree by the statements within thisdescription. The present embodiments may obviate one or more of thedrawbacks or limitations in the related art.

A method is disclosed for operating a robot. As part of this method, itis determined, if a difference between a current position or pose of therobot and a target position or pose of the robot exceeds a predeterminedthreshold value while the robot is in a torque-regulated operating mode.If, in particular only if, the difference exceeds the threshold value, apredicted model-based intermediate state, that the robot reaches beforethe target position according to the model, is determined, wherein aspeed of the robot in the intermediate state is lower than apredetermined speed threshold. When the robot reaches the intermediatestate, the robot is automatically switched from the torque-regulatedoperating mode to a position-regulated operating mode. The robot thenmoves into the target position in the position-regulated operating mode.

The robot may be an industrial robot, a lightweight robot, or arobotically moved tool or device. This means that an industrial robotfor use in production technology may be considered to be a robot justas, for example, a C-arm X-ray device held or mounted through and movedby a robot arm.

The position or pose, the speed, and/or the state of the robot may referto the corresponding parameter or value of the robot as a whole or ofany part or section of the robot, such as an end effector. A pose is tobe understood as a combination of a position and an orientation of therobot or a particular part thereof. A state of the robot may refer to orbe characterized by the position of the robot, one or more jointpositions or joint parameters, an orientation, and/or a speed orvelocity of the robot.

For maneuverability and for flexible application of the robot, the robotmay include at least one robot arm or manipulator, which in turn mayinclude multiple links connected through respective joints. The robotmay have multiple, (e.g., at least six), degrees of freedom (DOFs),which may correspond to the joints or axes of the robot or itsmanipulator.

To be able to determine the difference between the current position andthe target position, the current position may be continuously monitored,modelled, and/or simulated. For this purpose, the robot may include oneor more force sensors and/or torque sensors, which may provide sensordata as a basis for determining the current position. It is alsopossible to factor in a control signal sent to the robot and/or a stateof a drive of the robot, e.g., an expended drive power or engine outputof the robot, for determining the current position and/or the differencebetween the current position and the target position.

To determine the intermediate state, a motion of the robot may bemodelled using a full-fledged complete model of the robot or asimplified model may be used. A simplified model may advantageously beprocessed or evaluated more quickly and/or with less computationaleffort, thus enabling real-time application of the presently describedmethod. Because the speed of the robot is a main factor in determiningor selecting the intermediate state, other factors or parameters of thecomplete model might not be needed or may be modelled less precisely,while still enabling the simplified model to provide adequate data fordetermining the intermediate state. If, for example, an acceleration ofthe robot is relatively low, then determining the intermediate state ora corresponding point in time, at which the robot reaches the determinedintermediate state, with lower precision may be sufficient for themethod to work. Determining the intermediate state may include aninterpolation between different predetermined waypoints for the robotand/or between corresponding states. It may also be possible toextrapolate a current state and/or one or more past states and/or amotion leading up to the current position of the robot to determine orpredict the intermediate state.

In certain scenarios, the robot or the current position of the robot mayoscillate around the target position or a target trajectory withdecreasing amplitude while the robot is in the torque-regulatedoperating mode. Because of this, it may take a significant amount oftime for the robot to come to a standstill at or near the targetposition, as might for example be required for gripping or manipulatinga target object, such as a component part. By switching from thetorque-regulated operating mode to the position-regulated operating modebefore the robot has reached the respective target position, that is,while the robot is, for example, still oscillating around the targetposition, the present disclosure may enable the robot to come to astandstill or to reach the target position in a shorter time and/or withimproved positional accuracy. This may be the case, because moving therobot from its position at the intermediate state to the target positionin the position-regulated operating mode may advantageously preventfurther oscillations around the target position or an overshooting ofthe target position. It is a particular advantage of the presentdisclosure that this may be achieved without any negative effects orunrealistic effort, because the intermediate state is determined orselected in such a way, that, because of the corresponding speed of therobot being lower than the speed threshold, the switching between theoperating modes may be done smoothly.

In an advantageous development, an average contouring error, (e.g., acontouring error of the robot in the position-regulated operating mode),is used as the threshold value. The average contouring error may bepredetermined, for example, through testing by the manufacturer. Theaverage contouring error may, in other words, be provided as a knownvalue or input and/or as part of a specification of the robot. Using theaverage contouring error as the threshold value may be advantageous,because a corresponding tolerance needs to be considered anyway whenoperating the robot. If the difference between the current position andthe target position is smaller than the average contouring error, therobot may be switched between the different operating modes withoutissue, because even the more positional accurate position-regulatedoperating mode is only expected to position the robot at the targetposition with a precision defined by the contouring error. If, however,the difference between the current position and the target positionexceeds the average contouring error, then switching to theposition-regulated operating mode may reduce a momentary positionalerror.

In an advantageous development, the robot is also set to a higherstiffness setting than was used in the torque-regulated operating modewith or when switching to the position-regulated operating mode. Thismeans, that if and when the robot is operated in the position-regulatedoperating mode, the robot's stiffness is higher as compared to thestiffness of the robot if and when it is operated in thetorque-regulated operating mode. The change in stiffness and switchingbetween the operating modes may occur simultaneously. It is, however,possible for the change in stiffness to occur before or after switchingbetween the operating modes, in particular, on a timescale of anexecution of individual control commands. The higher stiffness orstiffness setting of the robot in the position-regulated operating modemay advantageously improve the positional accuracy and the robustnessagainst disturbances, so that the target position may be reached fasterand/or more accurate and/or be held more precisely.

In an advantageous development, the intermediate state is determinedbased on an interpolation of a motion of the robot between the currentposition and the target position. It may be advantageous to take intoaccount a path of the robot that it followed to reach the currentposition. For a more accurate and reliable interpolation, predeterminedconstraint limiting or defining possible motions or movements of therobot may be taken into account. If, for example, the robot is currentlymoving away from the target position, then the robot may notinstantaneously change its direction and move in an opposite directiontowards the target position without a deceleration phase. Here, forexample, a drive power of the robot and/or a mass of a load the robot iscurrently carrying may be taken into account.

The interpolation may be regarded as a simplified model of the robot orits motion. An interpolation between two fixed or known points may,however, be computed faster and easier than a complete model of therobot and its surroundings may be evaluated. Because the intermediatestate or the speed of the robot in the intermediate state do notnecessarily have to be known exactly, (as long as it is assured that thespeed of the robot in the intermediate state is lower than thepredetermined speed threshold), using the faster and easier to computeinterpolation for determining the intermediate state may advantageouslyenable the application of the presently described method even intime-constrained or time-sensitive situations and/or when the robot or arobotic system the robot is part of only have limited computing power.

In an advantageous development, the model used for determining theintermediate state is adapted and/or is chosen from multiplepredetermined models in dependence on a provided optimization criterion.The different adaptations or models may represent different strategiesfor operating the robot or for moving or guiding the robot into thetarget position. Each strategy may focus on or optimize for a differentgoal and/or constraint. This may advantageously allow for using thepresently described method in different situations, scenarios, or usecases. Especially advantageous optimization criteria may be a maximizedCartesian positioning accuracy, a maximized accuracy in axis space, amaximized rate of convergence to the target position, and/or minimizedjerk values of the motion of the robot.

The optimization criterion and therefore the corresponding adaptation ormodel to be used in a specific situation or instance may bepredetermined. It may then be provided as an input for the robot or acontrol unit of the robot or a corresponding robotic system, forexample, in dependence on a type of task or operation the robot isperforming. It may, however, also be possible to determine or select theoptimization criterion and/or the corresponding adaptation and/or modeldynamically during operation of the robot, for example, in dependence ona measured value for the difference between the current position and thetarget position, and/or a jerk value, and/or in dependence on themeasured or calculated rate of convergence to the target position.

Axis space is an abstract space, the dimensions of which may correspondto rotational and/or translational positions of the different axes ofthe robot or different rotational and/or translational positions ofcorresponding parts of the robot, such as a corresponding link of themanipulator, about the different axes of the robot.

While maximizing the positional accuracy and/or the accuracy in axisspace are self-evident advantages, maximizing the rate of convergence tothe target position may advantageously speed up an execution time of acurrent task of the robot, whereas minimizing the jerk values mayadvantageously improve handling of sensitive goods or loads, for exampleby reducing a risk of damaging them.

The different adaptations or models corresponding to the differentoptimization criteria may in turn correspond to, employ or includedifferent control or regulation strategies and/or, for example,different settings for the stiffness, a maximum speed, a maximumacceleration, a maximum rate of change of direction of the robot, and/orthe like. These different strategies and/or settings may be assumed ormodelled for determining the intermediate state. This may enable therobot or a corresponding data processing device or control unit toautomatically determine or select an optimum strategy and/or setting orset of settings. This may provide that the robot reaches an intermediatestate, in which the robot's speed is lower than the predetermined speedthreshold, before the target position. For this purpose, multipledifferent adaptations, models, strategies, and/or settings may beautomatically evaluated and corresponding outputs or outcomes may beautomatically compared.

A determined or selected adaptation, model, strategy, and/or setting maythen be provided to a control unit controlling or regulating the robot.The control unit may then implement or use the provided adaptation,model, strategy, and/or setting to provide that the predictedintermediate state is actually reached at all, in the modelled manner,and/or with a higher probability.

It is, however, also possible that the model used for determining theintermediate state is adapted and/or chosen based on a control orregulation strategy and/or a model currently used by the control unitand/or based on a current setting of the control unit and/or the robot.The currently used strategy, model, and/or setting or set of settingsmay be automatically retrieved from a corresponding storage device ofthe control unit or of the robot.

In an advantageous development, a motion of the robot in thetorque-regulated operating mode is modelled by modelling in torque spaceand in axis space a spring connecting the current position with thetarget position. An inflexion point of a motion of the springcorresponding to the motion of the robot is then determined as theintermediate state. A contraction and expansion of the spring may modelthe oscillation of the robot around the target position. Modelling thespring may therefore provide a simple to implement way for determiningan intermediate state with suitable conditions, e.g., an intermediatestate in which the speed of the robot is lower than the predeterminedspeed threshold. Because, at the inflexion point, the speed of thespring and therefore the corresponding speed of the robot (at least inone direction or dimension) is actually zero, the robot may be switchedbetween operating modes at this point without a need for a complextransfer function or transfer vector for transferring or transforming acurrent state of the robot between different controllers, control units,and/or control or regulation models of the robot. By modelling thespring in torque space as well as in axis space, the current position ofthe robot at the inflexion point is immediately available to enable aprecise operation of the robot in the position-regulated operating modewithout any delay.

In an advantageous development, a value for a mass of the robot and avalue for a mass of a load the robot is carrying are provided. Forswitching to the position-regulated operating mode, the current positionof the robot is calculated or computed based on the provided mass valuesand a torque value measured in the torque-regulated operating mode. Withthe known mass values, the measured torque may be converted into acurrent acceleration of the robot. This acceleration may then beconverted into a current axis position or current axes positions of therobot, thereby giving the current position or pose of the robot.

The robot may include one or more torque sensors for measuring thetorque value. It may be especially advantageous, if at least one torquesensor is arranged in each joint of the robot or at each axis of therobot. The mass of the load may be measured through a corresponding loadsensor of the robot or it may be provided as an external input. Bycalculating or computing the current position of the robot based onmeasured or externally provided (and therefore actual) values, thecurrent position may be determined more precisely than by relying on amodel or simulation of the robot, which may not take into account allexternal effects such as a mechanical tension affecting the robotthrough a mechanical contact with an external object. The improvedaccuracy or precision of the calculated or computed current position,which may be used as a starting point of the robot in theposition-regulated operating mode, may in turn enable a higherpositional accuracy of the robot in the position-regulated operatingmode for reaching the target position.

In an advantageous development, the robot is switched back to thetorque-regulated operating mode after the robot has reached the targetposition in the position-regulated operating mode. This means that the(then temporary) switch to the position-regulated operating mode betweenoperating times of the robot in torque-regulated mode may serve toimprove positional accuracy overall. While torque-regulation might beneeded for certain tasks or subtasks of the robot, there may be phasesor time-intervals during relatively long periods of torque-regulatedoperation, where the robot may advantageously be switched toposition-regulated operating mode for a part of this phase ortime-interval. This may improve the average positional accuracy and/orlower an execution time of the task or process carried out or performedduring the whole phase or time interval.

Another aspect of the present disclosure is a robotic system. Therobotic system includes a robot having multiple degrees of freedom, adata processing device, and a control device for controlling orregulating the robot in dependence on output data provided by the dataprocessing device. The data processing device is configured todetermine, if a difference between a current position of the robot and atarget position exceeds a predetermined threshold value while the robotis in a torque-regulated operating mode. The data processing device isfurther configured to determine a predicted model-based intermediatestate that the robot reaches before the target position according to themodel, so that a speed of the robot in the intermediate state is lowerthan a predetermined speed threshold. In particular, the data processingdevice is configured to determine the intermediate state, if or only ifthe difference between the current position of the robot and the targetposition of the robot exceeds the threshold value.

The data processing device may also be configured to determine and/orcontinuously or regularly track the current position of the robot andto, in particular, continuously, determine or calculate the differencebetween the current position and the target position. The dataprocessing device may be configured to provide the determinedintermediate state to the control device as the output data.

The control device is configured to automatically switch the robot fromthe torque-regulated operating mode to a position-regulated operatingmode when the robot reaches the intermediate state. The control deviceis further configured to steer the robot into the target position in theposition-regulated operating mode.

The data processing device and the control device or control unit may becombined or integrated into a single integrated device.

The robotic system, (e.g., the control device), may include multipleregulators for different operating modes of the robot or the roboticsystem may include different algorithms or models for controlling orregulating the robot according to different operating modes.

The robotic system, (e.g., the data processing device and/or the controldevice, may include at least one a processing unit (CPU) and/or astorage medium, wherein the respective storage medium may contain aprogram code or a part thereof designed or configured to perform amethod in accordance with at least one embodiment of the method onexecution of the program code by the processing unit. The processingunit may be or include one or more microprocessors and/or computerchips.

The robotic system may be configured to execute the method.

The embodiments and developments of the present disclosure describedherein for at least one aspect of the present disclosure, that is, forthe method and the robotic system, as well as the correspondingadvantages may be applied to any and all aspects of the presentdisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts an exemplary diagram illustrating differentbehaviors of a robot in different operating modes.

FIG. 2 schematically depicts an exemplary flow chart illustrating amethod for operating a robot.

DETAILED DESCRIPTION

Further advantages, features, and details of the present disclosurederive from the following description of embodiments as well as from thedrawings. The features and feature combinations previously mentioned inthe description as well as the features and feature combinationsmentioned in the following description of the figures and/or shown inthe figures alone may be employed not only in the respectively indicatedcombination but also in other combinations or taken alone withoutleaving the scope of the present disclosure.

FIG. 1 schematically depicts a diagram illustrating different behaviorsof a robot in different operating modes. An X-axis 1 of the diagramrepresents a stiffness or mechanical tension of the robot or affectingthe robot, while a Y-axis 2 of the diagram represents a positioningerror of the robot. The origin of the diagram, that is, minimal valueson the X-axis 1 and the Y-axis 2, represent a state of zero positioningerror and minimal stiffness or mechanical tension, such as duringunhindered movement of the robot through air.

A first operating domain 3 represents a behavior or possiblecharacteristics of the robot in an admittance control mode. Here, anexact positioning of the robot is achievable, in particular, if themotion of the robot is not hindered or influenced by a mechanicalcontact with an external object. With increasing stiffness, such as whenthe external object comes into contact with the robot and becomes moreand more difficult to move, the minimum achievable positioning error orpositional error of the robot increases.

A second operating domain 4 represents a behavior or characteristics ofa robot operated in an impedance control mode. In this impedance controlmode, the robot shows an opposite behavior or characteristic whencompared to the admittance control mode. In the impedance control mode,the minimum achievable positioning error is comparably large when themotion of the robot is not hindered or limited by a high stiffness,e.g., when the robot may freely move through air. If, however, the robotcomes into contact with a stiff external object, which may limit orprevent any drifting of the robot, the minimum achievable positioningerror of the robot decreases.

At medium stiffness values and medium to high positioning errors thefirst operating domain 3 and the second operating domain 4 overlap,meaning that corresponding behaviors or states of the robot may beachieved or may occur when using either one of the operating modes.

A region 5 in the diagram represents behaviors, characteristics, orstates which are not readily accessible using currently available robotcontrollers or regulators. Points along the X-axis 1 may be thought ofas representing a theoretically ideal robot or an ideal robot control oroperating mode, because it would be desirable to achieve zeropositioning error regardless of a stiffness or an external contact.

Because the positional error in the impedance control ortorque-regulated operating mode may be on the order of severalmillimeters or even centimeters, it may be desirable to use theadmittance control or position-regulated operation mode. Because certainapplications, such as a gripping a destructible object or joining, inparticular complexly shaped, component parts, may require thetorque-regulated operation mode, it is desirable to be able to switchbetween both operating modes.

FIG. 2 schematically depicts an exemplary flow chart 6 illustrating amethod for operating a robot using both a torque-regulated operatingmode and a position-regulated operating mode. In a process act S1, themethod is started. Here, the robot or a corresponding robotic systemincluding the robot, a data processing device and a control device, maybe activated. Also, a task and a target position for the robot may beprovided or acquired.

For the described example, the method is started with the robot beingoperated in torque-regulated operating mode. At this point, a continuousmonitoring of a current position of the robot may be activated or bealready active. This monitoring may remain active during the followingprocess acts.

For the present example, the robot may be an industrial robot taskedwith gripping a gear wheel from a supply, moving it to a targetposition, and from there assembling it into a gear mechanism. In afollowing task cycle the robot then moves via the target position backto the supply to grip the next gear wheel from the supply.

In a process act S2, a difference between the current position or poseand the target position or pose of the robot, in particular of an endeffector of the robot, is determined. This may be done through a simplecomparison.

In a process act S3, it is determined, if the difference between thecurrent position and the target position is greater than a predeterminedthreshold value. As indicated by a loop 7, the process acts S2 and S3may be continuously or regularly carried out or repeated.

If the difference between the current position and the target positionis greater than the threshold value, the method moves to a process actS4. Here, an intermediate state that the robot will or at least mayreach before the target position is determined based on a correspondingmodel or interpolation. A constraint for the intermediate state is thata speed of the robot in the intermediate state is lower than apredetermined speed threshold.

In order for the robot to be able to easily, precisely and reliably gripor pick the gear wheels from the supply and assemble the gear mechanism,a model, strategy and/or setting for maximizing a positional accuracymay be used. It may also be advantageous to use a model, strategy and/orsetting to enable a maximum rate of convergence to the target positionin the following acts of the method to improve efficiency of the robot.

When the robot reaches the determined intermediate state, it isautomatically switched from the torque-regulated operating mode to theposition-regulated operating mode in a process act S5.

In a process act S6, the robot then automatically moves to the targetposition in the position-regulated operating mode. This enables anespecially quick compensation of a positional error of the robot, whichmay not be reliably avoided during the previous torque-regulatedoperation of the robot.

The robot may be quickly and precisely brought or steered into thetarget position after assembling the currently transported gear wheelinto the gear mechanism. Precisely positioning the robot at the targetposition may advantageously provide that the robot does notunintentionally collide with any external object on its path back to thesupply, because the robot starts from a precisely known position, e.g.,the target position.

The robot may then move to the gear wheel supply. There it mayautomatically switch or be switched back to the torque-regulatedoperating mode in an optional process act S7 to enable a non-destructivegripping of the next gear wheel from the supply. Switching from theposition-regulated operating mode to the torque-regulated operating modemay be done more easily than switching in the opposite direction fromthe torque-regulated operating mode to the position-regulated operatingmode. This is the case, because in the position-regulated operating modethe robot is already precisely and reliably located at its respectivetarget position or on its respective intended or target path.

It is to be understood that the elements and features recited in theappended claims may be combined in different ways to produce new claimsthat likewise fall within the scope of the present disclosure. Thus,whereas the dependent claims appended below depend from only a singleindependent or dependent claim, it is to be understood that thesedependent claims may, alternatively, be made to depend in thealternative from any preceding or following claim, whether independentor dependent, and that such new combinations are to be understood asforming a part of the present specification.

While the present disclosure has been described above by reference tovarious embodiments, it may be understood that many changes andmodifications may be made to the described embodiments. It is thereforeintended that the foregoing description be regarded as illustrativerather than limiting, and that it be understood that all equivalentsand/or combinations of embodiments are intended to be included in thisdescription.

The invention claimed is:
 1. A method for operating a robot, the methodcomprising: determining, by a data processing device, a differencebetween a current position of the robot and a target position of therobot; identifying, by the data processing device, when the differenceexceeds a predetermined threshold value while the robot is in atorque-regulated operating mode; modelling a motion of the robot in thetorque-regulated operating mode by modeling in torque space and in axisspace a spring connecting the current position with the target position;determining, by the data processing device, a predicted model-basedintermediate state that the robot reaches before the target positionaccording to the model, wherein a speed of the robot in the intermediatestate is lower than a predetermined speed threshold; automaticallyswitching, by a control device, when the robot reaches the intermediatestate, the robot from the torque-regulated operating mode to aposition-regulated operating mode; and moving, by the control device,the robot into the target position in the position-regulated operatingmode.
 2. The method of claim 1, wherein the predetermined thresholdvalue is an average contouring error of the robot.
 3. The method ofclaim 1, wherein, in switching to the position-regulated operating mode,the robot is set to a higher stiffness setting than was present in thetorque-regulated operating mode.
 4. The method of claim 1, wherein theintermediate state is determined based on an interpolation of the motionof the robot between the current position and the target position. 5.The method of claim 1, wherein an inflection point of a motion of thespring is determined as the intermediate state.
 6. The method of claim1, further comprising: switching, by the control device, back to thetorque-regulated operating mode after the robot has reached the targetposition.
 7. A method for operating a robot, the method comprising:determining, by a data processing device, a difference between a currentposition of the robot and a target position of the robot; identifying,by the data processing device, when the difference exceeds apredetermined threshold value while the robot is in a torque-regulatedoperating mode; determining, by the data processing device, a predictedmodel-based intermediate state that the robot reaches before the targetposition according to a model, wherein a speed of the robot in theintermediate state is lower than a predetermined speed threshold;automatically switching, by a control device, when the robot reaches theintermediate state, the robot from the torque-regulated operating modeto a position-regulated operating mode; and moving, by the controldevice, the robot into the target position in the position-regulatedoperating mode, wherein, in dependence on a provided optimizationcriterion, the model used for determining the intermediate state isadapted from multiple predetermined models, chosen from the multiplepredetermined models, or a combination thereof.
 8. The method of claim7, wherein the provided optimization criterion is a maximized Cartesianpositioning accuracy, a maximized accuracy in axis space, a maximizedrate of convergence to the target position, minimized jerk values of themotion of the robot, or a combination thereof.
 9. The method of claim 7,wherein the predetermined threshold value is an average contouring errorof the robot.
 10. The method of claim 7, wherein, in switching to theposition-regulated operating mode, the robot is set to a higherstiffness setting than was present in the torque-regulated operatingmode.
 11. The method of claim 7, wherein the intermediate state isdetermined based on an interpolation of a motion of the robot betweenthe current position and the target position.
 12. The method of claim 7,wherein a motion of the robot in the torque-regulated operating mode ismodelled by modelling in torque space and in axis space a springconnecting the current position with the target position, and wherein aninflection point of a motion of the spring is determined as theintermediate state.
 13. The method of claim 7, further comprising:switching, by the control device, back to the torque-regulated operatingmode after the robot has reached the target position.
 14. A method foroperating a robot, the method comprising: providing a value for a massof the robot and a value for a mass of a load the robot is carrying;determining, by a data processing device, a difference between a currentposition of the robot and a target position of the robot; identifying,by the data processing device, when the difference exceeds apredetermined threshold value while the robot is in a torque-regulatedoperating mode; determining, by the data processing device, a predictedmodel-based intermediate state that the robot reaches before the targetposition according to a model, wherein a speed of the robot in theintermediate state is lower than a predetermined speed threshold;automatically switching, by a control device, when the robot reaches theintermediate state, the robot from the torque-regulated operating modeto a position-regulated operating mode, wherein, for the switching tothe position-regulated operating mode, the current position of the robotis calculated based on the provided mass values of the robot and theload and a torque value measured in the torque-regulated operating mode;and moving, by the control device, the robot into the target position inthe position-regulated operating mode.
 15. The method of claim 14,wherein the predetermined threshold value is an average contouring errorof the robot.
 16. The method of claim 14, wherein, in switching to theposition-regulated operating mode, the robot is set to a higherstiffness setting than was present in the torque-regulated operatingmode.
 17. The method of claim 14, wherein the intermediate state isdetermined based on an interpolation of a motion of the robot betweenthe current position and the target position.
 18. The method of claim14, wherein a motion of the robot in the torque-regulated operating modeis modelled by modelling in torque space and in axis space a springconnecting the current position with the target position, and wherein aninflection point of a motion of the spring is determined as theintermediate state.
 19. The method of claim 14, further comprising:switching, by the control device, back to the torque-regulated operatingmode after the robot has reached the target position.
 20. A roboticsystem comprising: a robot having multiple degrees of freedom; a dataprocessing device; and a control device for regulating the robot independence on output data provided by the data processing device,wherein the data processing device is configured to: determine adifference between a current position of the robot and a target positionof the robot, identify when the difference exceeds a predeterminedthreshold value while the robot is in a torque-regulated operating mode,model a motion of the robot in the torque-regulated operating mode bymodeling in torque space and in axis space a spring connecting thecurrent position with the target position, and determine a predictedmodel-based intermediate state, that the robot reaches before the targetposition according to the model, wherein a speed of the robot in theintermediate state is lower than a predetermined speed threshold, andwherein the control device is configured to: automatically switch therobot from the torque-regulated operating mode to a position-regulatedoperating mode when the robot reaches the intermediate state, and steerthe robot into the target position in the position-regulated operatingmode.